In the past, certain types of electrical and electro-mechanical equipment have been provided with proximity detectors for controlling the movement of potentially injurious moving parts in response to the approach of a portion of a human body such as a hand or arm. An example of such a proximity detector is disclosed in U.S. Pat. No. 4,453,112 issued to Saver et al, and this proximity detector is operative to stop the motion of automatic automobile windows in response to human body capacitance reaching a predetermined critical distance from a moving window glass. U.S. Pat. No. 4,453,112 is incorporated herein by reference.
However, as presently known, hazardous electrical equipment requiring the presence of an operator in relatively close proximity to potentially dangerous moving parts, such as saw blades, has not been equipped with protective devices for rapidly shutting down the equipment when the operator's hands or arms reach a critically dangerous distance from the moving parts. Where body capacitance-operated proximity sensitive devices have been utilized to control certain types of electrical and electro-mechanical equipment, problems have developed with the inability of these devices to discriminate between human body motion on the one hand and the motion of inanimate objects on the other hand. Thus, the desirability of providing a highly sensitive and discriminating proximity safety device and system for the protection of operators of dangerous equipment is manifest.